The present invention claims priority and contains subject matter related to Japanese Patent Application No. 2000-011207, filed in the Japanese Patent Office on Jan. 20, 2000, the entire contents of which is incorporated by reference herein.
1. Field of the Invention
The present invention generally relates to either an image forming apparatus, such as a copying machine, a printer, a facsimile, etc., or a multi-functional image forming apparatus and more particularly, to an electrophotographic image forming apparatus, wherein a toner image is formed on a photo-receptor so that by repeating an image forming process, including charging, image writing, developing, transferring, cleaning, discharging, etc., the toner image is transferred to a recording medium directly or via an intermediate transfer member.
2. Discussion of the Background
In an image forming apparatus employing an electrophotography process, such as a copying machine, a printer, a facsimile, or similar, an increasing number of the image forming apparatuses are made compact by employing a process cartridge, wherein a photo-receptor, a charging device, a developing device, etc. are integrally accommodated in a case.
With the demand for reducing the size of the image forming apparatus, the process cartridge has been made more compact. Consequently, a discharging device is likely to be arranged outside of the process cartridge due to a lack of space in the process cartridge.
As illustrated in FIG. 6, when a discharging device 1 is arranged inside of a process cartridge 2, light, indicated by a reference character L1 and emitted from the discharging device 1, passes through aback side of a charging device 3. Further, the light L1 is reflected by an inner surface of a cartridge case 4 of the process cartridge 2 and then, a surface of a photo-receptor 5 is irradiated with the light L1.
The above-described light L1 causes a problem because a charged potential of the surface of the photo-receptor 5, which is uniformly charged by the charging device 3, is changed due to the irradiation of the light L1. The above-mentioned problem is solved by arranging the discharging device 1 outside of the process cartridge 2.
However, as illustrated in FIG. 7, when the discharging device 1 is arranged outside of the process cartridge 2, because the discharging device 1 is apart from the photo-receptor 5, the amount of light, emitted from the discharging device 1 to the photo-receptor 5, needs to be increased.
When the amount of light emitted from the discharging device 1 increases, the light from the discharging device 1 is likely to scatter. As a result, light, indicated by a reference character L2, passes through a relatively large cutaway portion of the cartridge case 4 and then, the surface of the photo-receptor 5, which is located immediately before a position B, where the charging device 3 charges the surface of the photo-receptor 5 (hereinafter referred to as a charging position B), is directly irradiated with the light L2. Thereafter, when the irradiated surface of the photo-receptor 5 is charged by the charging device 3, the charged potential of the surface of the photo-receptor 5 becomes low.
Further, when the light, emitted from the discharging device 1, scatters, the surface of the photo-receptor 5, which is located immediately before the charging position B, is irradiated with a light indicated by a reference character L3, emitted from the discharging device 1, and reflected by a cleaning blade 7 of a cleaning device 6. In such a case, when the irradiated surface of the photo-receptor 5 is charged by the charging device 3, the charged potential of the surface of the photo-receptor 5 also becomes low.
Furthermore, when the light, emitted from the discharging device 1, scatters, the surface of the photo-receptor 5, which is located immediately before the charging position B, is irradiated with a light indicated by a reference character L4, emitted from the discharging device 1, first reflected by the surface of the photo-receptor 5 and then, reflected by the cleaning blade 7 of the cleaning device 6. Similarly, as in the above-described two cases, when the irradiated surface of the photo-receptor 5 is charged by the charging device 3, the charged potential of the surface of the photo-receptor 5 becomes low.
The above-described lowering of the charged potential of the surface of the photoreceptor results in deterioration of image quality.
The present invention has been made in view of the above-discussed and other problems, and an object of the present invention is to address these and other problems.
Accordingly, another object of the present invention is to provide a novel electrophotographic image forming apparatus, wherein lowering of a charged potential of a surface of a photo-receptor, which is caused by irradiating the surface of the photo-receptor, located immediately before a charging position, with a light emitted from a discharging device, can be prevented.
These and other objects are achieved, according to the present invention, by providing a novel electrophotographic image forming apparatus that includes: a process cartridge, including at least a photo-receptor, on which a toner image is formed, and a charging device, configured to uniformly charge a surface of the photo-receptor; and a discharging device, provided outside of the process cartridge and configured to emit light to discharge the surface of the photo-receptor. The process cartridge includes a light incidence opening to pass the light emitted from the discharging device therethrough. The light incidence opening is formed to regulate the passed light so as to irradiate an area of the surface of the photo-receptor.
The irradiated area of the surface of the photo-receptor may be outside of an area of the surface of the photo-receptor, within 5 mm from a position where the charging device charges the surface of the photo-receptor, at an upstream side of the position.
Other objects, features, and advantages of the present invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings.